(optional) Delete any packages you do not want installed. For example, you may wish to delete the fonts, onlineupdate, or math packages.

(optional) Prevent yum from upgrading OxygenOffice to Fedora's OpenOffice.org:
su -c "echo exclude=openoffice*>>/etc/yum.conf"
If you already have excluded packages, you'll need to use an editor instead of this command.

To fix the error, just replace OxygenOffice's private libxml2 with the one from Fedora. The version numbers may differ slightly, so make sure to adjust them as needed. There are several /usr/lib/libxml2.so.* files, so choose the file with the longest name and the largest size. (The rest are symlinks.)
sudo cp /usr/lib/libxml2.so.2.6.31 /opt/openoffice.org2.3/program/libxml2.so.2.6.17